Method and device for driving step-by-step electrical rotary machine

ABSTRACT

An electrical rotary machine comprising a stator and a rotor may be used as a step motor when the outputs of a digital phase modulator comprising a clock pulse generator and pulse number reducing circuits each comprising a chain of flip-flops connected in series are applied to the stator and the rotor windings through an inverter respectively to generate the rotating magnetic fields. In response to a number of rotation command pulses to be inserted in a clock pulse train from the clock pulse generator and to a manner by which the command pulses are inserted into the clock pulse train, a number of steps and the direction of rotation of the rotor can be controlled. The angle of rotation of the rotor in response to one command pulse may be varied by varying a number of series-connected flip-flops in the pulse number reducing circuit.

United States Patent 11 1 Takaiet at.

Hasegawa, Yokohama; Michio Nakano, Tokyo, all of Japan [73] Assignee: President of Tokyo Institute of Technology, Tokyo, Japan 22 Filed: Mar.10,1972

[21] Appl. No.: 233,619

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 12/1967 McDonough et al. 318/608 X 7/1959 Bekey 318/187 X 7 l CLOCK PULSE GENERATOR PULSE FOR I fiifii ROTAT|ON l 52 o l GATE INVERTER CIRCUIT COMMAND PULSE FOR POSITIVE ROTATION [451 Nov. 27, 1973 2,168,170 8/1939 Mittag 318 187 x 2,537,427 1 1951 Seid et al... 318/608 2,824,272 2/1958 Delaporte 318/187 x 3,374,359 3/1968 Anderson 310/608 3,421,061 1/1969 Baughman 318/187 x Primary Examiner-G. R. Simmons Attorney-Milton J 7 Wayne et al.

57 ABSTRACT An electrical rotary machine comprising a stator and a rotor may be used as a step motor when the outputs of a digital phase modulator comprising a clock pulse generator and pulse number reducing circuits each comprising a chain of flip-flops connected in series are applied to the stator and the rotor windings through an inverter respectively to generate the rotating magnetic fields. In response to a number'of rotation command pulses to be inserted in a clock pulse train from the clock pulse generator and to a manner by which the command pulses are inserted into the clock pulse train, a number of steps and the direction of rotation of the rotor can be controlled. The angle of rotation of the rotor in response to one commandpulse may be varied by varying a number of series-connected fliptlops in the pulse number reducing circuit.

6 Claims, 7 Drawing Figures lNVERTER PATENTED W 7 3 sum 3m 3 FIG. 6

R D I 2 2M El I I l T M S I F F F A u l U DE 0 O 0 OT P NVv T T T TU K Al T U .U UOE C MT P DI DIHS O l U T T TT L W% 7 P U U U C CP W O O OWP FIG. 7

WITHOUT COMMAND PULSE wN F0 7 I I 2 2 fin I H F F F LT E UO F F F F U DE 0 O Du NW T T T K T U U U M T P P P C M U T T T W. 0% P ,U U U C CN W O O O 1 METHOD AN D DEVICE. FOR Ell-WING STEI BY-SPIEP ELECTRICAL ROTARY MACHINE BACKGROUND OF INVENTION The present invention. relates to at methodand a de-= vice for driving s'tep-by-step an electricall rotary ma- -chine and more particularly an electrical rotar ymachine. comprising a stator andi rotori'both carryingzpolyphase windings.

Ingeneral, the prior. art stepping: motors have a: con struction comprising a salient pole rotor: havingarplii rality of teeth anda stator havinggaeplurality of teeth 2? flopsor' pulse number reducing means and an inverter connected? in series; These power. source circuitsare called the digital*- phasemodulators. The AC voltages appear at the'outputs' of. the inverters" in response to the outputs of the series-connected; flip-flop circuits to whicli'areapplied the outputioftlieclock pulse generator. Theoutputs of the fli'p*flop-circuits= arevapplied to the" windings ont he stator and rotor through each of the inverters. The rotor is: locked in a: position correl0 sponding-jtothe difference in phaseof the AC voltages corresponding. to the salient poles ofi the rotor formed to one input pulse is determined solely-depending upom the mechanical constructions ofstherotor and 'the: stator, and a circuit which is extremely complicatedin construction has been required. to vary'the. angle of rotation of the rotor in response. to: one. input-pulse: Therefore, the variation and control:ofitheaartgleiof ro-- tation of the rotor in responseto oneinputpulsehas have been virtually difficult to obtain in the prior-art stepping motors.

SUMMARY OF'THE m annon.

One of the objects of thepresent invention is to provide a method and a device for permittinga. generalt electrical rotary machine to be used as asteppingmotor. A

capable of producing. a .high output.

Another object of the present invention is to provide a method and a device capableof changing. arbitrarily anangle of rotation of the rotor by simple-imeansin' response to one input pulse.

A further object of the presentinventionxis'to provide a system and a device which is simple imconstruction. and operation for driving step-by-stepqan electrical rotary machine.

According to the present invention, an electricalro-- tary machine comprising a stator and arotoreachihaw Anothe robject ofthe present invention istoprovides a stepping. motor which is simple in construction: but;

imresponse to one-command pulse'may be electrically ing the identical polyphase windings may be'usedasa stepping motor; The phase. of the AC voltage applied to one of the stator and therotor isshifted withrespect to the reference phase of the AC voltagerappliedato the other in proportion to a number of command pulses so that the angle of rotation of the rotor is proportionaltto the-number of command pulses.

According to one aspect of the present invention, the

stator or rotor is supplied withthe AC voltage froma.

powersource circuit comprisinga clock pulsergenerator, a plurality of flip-flops'or pulsenumberreducing;

means and an inverter connec'tedain"series; On thew v other hand, the rotor orstator is-supplied'awithethe-AC voltage from a power. source circuit comprisingig-thea clock pulse generator, a gate circuit, aplurality of flip age. supplied? applied? to the stator and rotor. When a number of pulses'areapplied to tlie power'source circuit including" the" gate, the: output AC voltage ofthis circuit: is adva'ncedron lagged; in phase" With 'r'espect to the volt- I th powerso'urce circuit-withouta gate y'l hereforep otor'is caused torotatestep bystep through am angler correspondingto= the phase dif ferencef betweens the. two. AC voltages; That is, a numbenofs steps-made"? by the roto r iscontrolled" in: response toia.numbenofipulses applied tothegate, and? the angle of rotation of l the rotor in response to" one commandpulse canrbewaried by changingsthe number of seriesconnectedbflip-flopsa One ofi'thez=noveliadvantages of the present invention resides in the facts'that a convention al' electrical rotary machine:comprisingfa vstator and: a rotor both carrying the'polyphasev windingsrmaybe used as: a stepping motor. Therefore; theqsteppinggmotor"inaccordance with the: presentsinvention is I extremely simplified in con.- struction-.as comparednwith the prior art steppingtmotors: Furthermore; whenitheeroton is lockedin position; no current, flows except the. current for exciting v the magneticcircuitsasin theecase-offal-transformer, so that theundesiredi heating problem can be eliminated and tlrexpower consumption may. be lowered. In theprior artstepping'motors, the angle of rotation of the rotor in: response: to an input'signal is dependent solely upon their mechanical?construction; However, aecordingtothe: present invention, the angleof-Totation of the rotor varied by a controlunit.

The aboveandother objects, features. and advantagesof thetpresent invention 'will becomemore apparent from the followingidescription of the preferred embodiments thereof taken in conjunction with the accompanyingvdrawingi;

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG'J isadiagrammatic .view illustrating-a two-phase induction:- motor towhich is applied the present invention;.

FIGSiZ 'and 3. are: views usedv for explanation of theprincipleof the present. -invention,'. FlGlr-showing the case: when the output: torque is zero whereas FIGLS:

showing the-casewhen the torquein' the clockwise: di rectionxisz-produced;

FIG-1.4 isxa-block-diagram of a control unit in: accor dance-with the. present invention; and

FIGS;5 7' are-views illustrating various -waveforms at variouspoints;in-the*controlunit-shownainFIGAfor-em planation of the-mode ofbperation thereofi DESCRIPTION OFTHE PREFERRED.

EMBQDIMENT I Firstlthe:principleofthepresentsinvention will be described; It; is assumed that thepresent invention-be applied: to a. two-phaseinduction motor which, as dia- 3 grammatically shown in FlG.l, comprises a stator 1 carrying (a reference and control) windings 1M and 1A and a wound rotor 4 carrying windings 4M and 4A. Because of series-connected capacitors 2 and 5, these windings 1A and 4A are supplied with the voltages 90 5 out of phase with the voltages supplied to the windings 1M and 4M from voltage sources 3 and 6 respectively.

Referring'to FIG.4, a control unit of the present invention, which is for permitting the two-phase induction motor of the type shown in FlG.1 to be used as a step motor, comprises a clock pulse generator 7, a gate circuit 8, a first chain of flip-flops 9, l0 and 15 and an inverter 13, which is the source 3 shown in FlG.l, a second chain of flip-flops 11, 12 and 16, and an inverter 14 which is the source 6 shown in F101 for supplying the voltage to the rotor 4. These inverters l3 and 14 are adapted to supply the AC voltages to the stator l and to the rotor'4, respectively, in synchronism with theoutputs from the flip-flops 10 or 15 and 12 or 16, respectively. The flip-flops 15 and 16 may be selectively inserted between the flip-flop 10 and the inverter 13 and between theflip-flop l2 and the inverter 14, respectivelyvby switches S and S, as will be described in more detail hereinafter. Although the first and second chains of flip-flops are shown as consisting of three flipflops, the number of flip-flops in each chain may be increased or decreased so that the angle of rotation of the rotor 4 in response to one command pulse may be arbitrarily selected in a manner to be described hereinafter.

Next referring to H082 and 3, when the stator and rotor voltages are in phase as shown at B and C in F102, and if the initial mechanical angle 0 between the stator and rotor windings is zero, and rotating magnetic fields rotate in the same direction as indicated by the arrows X and Y at the same angular velocity and in the same phase, the poles N and S of the stator l are in opposition to the poles S and N of the rotor 4. Consequently the rotor 4 is not rotated and remains in a locked position. I

When the voltage supplied from the source 6 lags by an electrical angle 0,; behind the voltage supplied from the source 3 tothe stator winding as shown in FlG.3, the rotating magnetic field which is set by the rotor winding lags by 0,; behind the rotating magnetic field generated by the stator winding, so that the torque is produced to turn the rotor 4 in the clockwise direction in order to eliminate this phase difference 0,; between the two rotating magnetic fields as shown in FIG.3. As a result, the rotor 4 rotates in the direction indicated by Z through an angle given by where p the number of pairs of poles which equals P/2 where i P is the number of poles. k

From the foregoingdescription of the principle of the present invention, it is now clear that thetwo-phase in duction motor can be used as a step motor, and next the mode of operation of this step motor will be described in more detail with reference to FIGS.4 arid 5.

For the sake of explanation, it isv assumed that the initial mechanical angle between the stator and rotor windings is zero as shown in FIG.2A, and that the AC voltages in phase be initially supplied to the stator and rotor windings. As described hereinbefore, the AC voltages are supplied from the inverters l3 and 14 in response to the outputs from the flip-flops 10 and 12 respectively. The waveforms of the voltages at various points in the control unit are shown in FlG.5.That is, the outputs as shown at A and B in FIGIS'are derived from the flip-flops 9 and 11 and from 10 and 12, respectively, in response to the clock pulse train from the clock pulse generator 7. It should be noted that, asis well known in the art, the pulse duration of the outputs from the flip-flops 10 and 1 l is twice that of the outputs from the flip-flops 9 and 1 1 and that the pulse duration is further doubled when another flip-flop is added in series. Thus, the windings 1M and 4M of the stator and the rotor are supplied with the voltage shown at D in FIG.5, whereas the windings 1A and 4A, the voltages shown at E'in FlG.5.

When a positive rotation command pulse is applied to the gate 8, it is added into'the clock pulse train supplied to the flip-flop 1-1 as shown at C in F [6.6 so that the phase of the voltage supplied to the rotor 4 leads by an angle corresponding to one pulse relative to the phase of the voltage supplied to the stator 1. As a result, the rotor 4 is caused to rotate stepwise to eliminate this phase difference in the manner described above, and is stopped and locked in position when this phase difference has been eliminated. On the other hand when a negative rotation command pulse is applied to the gate 8, one pulse is cancelled from the clock pulse train supplied from the clock pulse generator 7 to the flipflop 11 as shown at B and C in FIG]. As a result, the phase of the voltage applied to the rotor 4 lags behind that of the voltage supplied to the stator 1 by an angle corresponding to one pulse, so that the rotor 4 is caused to rotate in the counterclockwise direction through 0 which is equal to 6 /p and is locked in position in the manner similar to that described above.

From the foregoing description, it is seen that the gate 8 serves as an adder circuit when the positive rotation command pulse is applied and as a subtraction circuit when the negative rotation command pulse is applied, so that the digital control of the angle of rotation of the rotor in response to the positive or negative command signals applied to the gate 8 becomes possible. That is, in response to the positive or negative command pulse applied to the gate 8, the phase of the voltage applied to the rotor 4 leads or lags by an angle corresponding to one command pulse relative to the phase of the voltage applied to the stator l. The phase difference 0 caused by one command pulse is given by 0,; 211' 1/2" (radians) scribed. When the moving contacts of the switches S and S are switched from the fixed contacts a to the fixed contacts b, these flip-flops 15 and 16 are connected in series with the flip-flops 9 and 10 and 11 and 5 12 respectively. This means, the number of the series connected flip-flops in each voltage supply circuit is increased by one so that the angle of rotation of the rotor is decreased by one half. It is seen that as one additional flip-flop is added, the angle of rotation is further reduced by one half from the above equation.

. What is claimed is:

l. A method for driving step-by-step an electrical rotary machine comprising the steps of applying polyphase AC voltages generated in synchronism with the pulses in a clock pulse train to the polyphase windings on a stator and a rotor of an electrical rotary machine so as'to generate the rotating magnetic fields,

inserting a number of rotation command pulses into said clock pulse train to be applied to one of said stator and rotor so as to vary the phase of the voltage applied to said one of said stator and rotor with respect to the phase of the voltage applied to the other, and varying the phase of the rotating magnetic field on said one of said stator and rotor stepby-step, thereby causing said rotor to rotate stepby-step.

2. A method for driving step-by-step an electrical rotary machine set forth in claim 1 comprising controlling the number of steps made by said rotor in response to a number of said rotation command pulses.

3. A method for driving step-by-step an electrical rotary machine set forth in claim 1 comprising generating said polyphase AC voltages by a circuit connected in series to a circuit comprising a predetermined number of circuits for reducing pulses so that the angle of rotation of said rotor in response to each of said rotation command pulses may be controlled by the number of said pulse number reducing circuits.

4. A device for driving step-by-step an electrical rotary machine having a stator and rotor with polyphase windings, comprising a clock pulse generator means,

a first AC voltage generator circuit comprising a first series-connected circuit connected in series to the output of said clock pulse generator means and comprising a predetermined number of pulse number reducing means, and an'AC voltage generator means connected in series to the output of said first series-connected circuit;

a second AC voltage generator circuit comprising a rotation command-pulse-control gate connected inseries to the output of said clock pulse generator means,

a second series-connected circuit connected in series to the output of said gate and comprising a predetermined number of pulse counting means, and an AC voltage generator means connected in series to the output of said second seriesconnected circuit,

means applying the outputs of said first and second AC voltage generator circuits to the polyphase windings of said stator and a rotor of said electrical rotary machine respectively so that the rotating magnetic fields may be produced by said polyphase windings of said stator and said rotor respectively; whereby the angle and direction of rotation of said rotor are controlled in response to a number of said rotation-command-pulses and to a manner by which said rotationcommand-pulses are applied.

5. A device for driving step-by-step an electrical rotary machine set forth in claim 4 wherein said first and second AC voltage generator circuits further comprise means for changing the number of said pulse counting means. I

6. A device for driving step-by-step an electrical rotary machine set forth in claim 4 wherein said pulse number reducing means comprise flip-flops. 

1. A method for driving step-by-step an electrical rotary machine comprising the steps of applying polyphase AC voltages generated in synchronism with the pulses in a clock pulse train to the polyphase windings on a stator and a rotor of an electrical rotary machine so as to generate the rotating magnetic fields, inserting a number of rotation command pulses into said clock pulse train to be applied to one of said stator and rotor so as to vary the phase of the voltage applied to said one of said stator and rotor with respect to the phase of the voltage applied to the other, and varYing the phase of the rotating magnetic field on said one of said stator and rotor step-bystep, thereby causing said rotor to rotate step-by-step.
 2. A method for driving step-by-step an electrical rotary machine set forth in claim 1 comprising controlling the number of steps made by said rotor in response to a number of said rotation command pulses.
 3. A method for driving step-by-step an electrical rotary machine set forth in claim 1 comprising generating said polyphase AC voltages by a circuit connected in series to a circuit comprising a predetermined number of circuits for reducing pulses so that the angle of rotation of said rotor in response to each of said rotation command pulses may be controlled by the number of said pulse number reducing circuits.
 4. A device for driving step-by-step an electrical rotary machine having a stator and rotor with polyphase windings, comprising a clock pulse generator means, a first AC voltage generator circuit comprising a first series-connected circuit connected in series to the output of said clock pulse generator means and comprising a predetermined number of pulse number reducing means, and an AC voltage generator means connected in series to the output of said first series-connected circuit; a second AC voltage generator circuit comprising a rotation command-pulse-control gate connected in series to the output of said clock pulse generator means, a second series-connected circuit connected in series to the output of said gate and comprising a predetermined number of pulse counting means, and an AC voltage generator means connected in series to the output of said second series-connected circuit, means applying the outputs of said first and second AC voltage generator circuits to the polyphase windings of said stator and a rotor of said electrical rotary machine respectively so that the rotating magnetic fields may be produced by said polyphase windings of said stator and said rotor respectively; whereby the angle and direction of rotation of said rotor are controlled in response to a number of said rotation-command-pulses and to a manner by which said rotation-command-pulses are applied.
 5. A device for driving step-by-step an electrical rotary machine set forth in claim 4 wherein said first and second AC voltage generator circuits further comprise means for changing the number of said pulse counting means.
 6. A device for driving step-by-step an electrical rotary machine set forth in claim 4 wherein said pulse number reducing means comprise flip-flops. 